Canister Filter

An external sealed filter unit that pulls tank water through multiple media stages - the gold standard for medium-to-large freshwater tanks.

Price: Mid For: Both $80-$400

📖 Overview

A canister filter sits below the tank, connected via intake and return hoses. Water passes through customizable media stacks - mechanical, chemical, biological - providing excellent water quality with modest flow noise. Popular for planted tanks and larger community setups.

🎯 Purpose

Combined mechanical (traps debris), biological (nitrifying bacteria colonization), and chemical (activated carbon, phosphate remover) filtration.

⚙️ How It Works

Pump draws water from the tank, pushes it through progressive media layers, and returns clean water via a spraybar or lily pipe. Fully sealed system means the water is under pressure and cannot spill.

⏰ When Needed

Tanks over 30 gallons. Planted tanks (for adjustable flow via spraybar). When silent operation matters. When you want customizable filter media choices.

✅ Pros

Highest water throughput per size. Very quiet operation. Enormous media capacity. Adjustable flow. Easy media customization.

❌ Cons

Setup complexity higher than HOB. Priming required. Leak potential if seals fail. Higher upfront cost.

🏷️ Top Brands

Eheim (German, industry gold standard), Fluval, OASE, SunSun (budget), Fx-series by Fluval for large tanks.

🧰 Maintenance

Rinse mechanical media in tank water monthly. Replace chemical media (carbon, phosphate) every 4-6 weeks. Bio-media rinses every 6-12 months. Check hoses and seals annually.